1. Field of the Invention
The present invention relates to a tag access control system, a tag access control method and a tag access control program for controlling data communication between IC tags provided in moving articles and a plurality of reader/writers.
2. Description of Related Art
In recent years, attention has been given to an RFID (Radio Frequency Identification) technology for recognizing an article using an IC tag. For example, in a factory or a distribution center, articles such as components or products are transported by a belt conveyor, a forklift, a truck or the like. By providing such articles with IC tags, it is possible to identify and manage the transported articles. In particular, passive-type IC tags require no batteries, so that the reduction of size and price can be achieved. Accordingly, they are expected to suit the identification and management of a large volume of articles.
The passive-type IC tag exchanges data by radio with a reader/writer having an antenna. In the case where the reader/writer reads data from and writes data into the IC tag attached to a transported article, an access to the moving IC tag is sometimes necessary. However, in the data communications with the moving IC tag, a failure rate of reading and writing rises sharply when the moving velocity of the IC tag is increased to or above a certain value. Therefore, it has been necessary to stop moving the articles temporarily within a communicable range of the antenna or move the articles at a sufficiently low velocity at the expense of turnover. Under such circumstances, there has been a need for a technology that improves an entire efficiency without lowering the velocity of moving the articles to which the tags are attached.
Conventionally, in order to read and write data as quickly as possible, technologies of the reader/writer (R/W) and the antenna have been developed for shortening the time required for data communications and the reading and writing time of IC tags. However, there has been a limit to processing capacities of a single reader/writer and a single antenna.
Accordingly, JP 2004-82432 A, for example, has disclosed a label printer that uses a plurality of reader/writers, thereby reducing a writing failure rate while maintaining a recording velocity. In this label printer, if one reader/writer fails to write data in an IC tag, the other reader/writer writes the data therein again. Also, in the case where data to be written are equal to or larger than a certain size, the plurality of reader/writers write divided data in an IC tag.